How to Dry Polymer Clay

Polymer clay, a poly-vinyl chloride clay mixed with diluents and colors, dries by baking in the oven. Not to be confused with modeling clay, which never hardens -- or self-hardening clays that dry with exposure to air -- polymer clays bake at temperatures between 215 and 325 degrees Fahrenheit depending on which company’s clay you use.

Bake a Sample Piece

When you haven’t baked polymer clay before, roll out a sample piece 1/4 inch thick and bake it in the oven as per the package’s recommended times, which can range from 10 to 30 minutes based on the clay’s manufacturer. You need an accurate oven thermometer to ensure the temperature of the oven is correct, which you can buy separately and set inside the oven or hang from a rack. After baking the sacrificial piece, cool it in ice water so that you can handle it. Cut it open to check the inside for crumbling -- an indication that the clay did not cook long enough.

Glazed Ceramic Surface

Use a 12- or 6-inch glazed ceramic tile from the local home improvement store on which to bake your project piece in the oven. The glazed tile -- already cured in a kiln at higher temperatures than your oven can reach -- retains heat to allow your clay item to bake evenly, even when you open the oven door to check periodically. If you overcook your clay item, it may turn brown or scorch, which you can correct by sanding or painting over it.

Preheat the Oven

Preheat the oven to the exact temperature required and bake as per the recommended time on the product’s packaging. Once the oven reaches the desired temperature, set the project piece on the glazed ceramic tile into the center of the oven. Thicker pieces require longer baking times, which is why you may want to bake a sample at the thickness of your project first to test how long it takes to bake it.

Add Time Based on Thickness

Polymer clay crafters treat the standard thickness as 1/4 inch and add additional minutes per this measurement according to the baking times the manufacturer lists for thicker pieces. For example, one product's directions recommends baking at 275 degrees Fahrenheit for 15 minutes for each 1/4 inch. In this example, a 1-inch-thick polymer clay project takes 60 minutes to bake. After the item has thoroughly baked, don’t touch it, as it will be hot and soft to the touch. It hardens more as it cools. With the proper heat-resistant baking gloves, remove the item from the oven and set it on a hot pad for it to cool.

Tips and Considerations

Translucent or light-colored clays can scorch at recommended temperature settings. Reduce the oven temperature by 10 degrees and bake the item twice as long or bake a sample piece to test times and temperatures. In you live above 3,500 feet, bake for 10 minutes longer and add 5 degrees to the oven setting. For ovens that heat up quickly at higher temperatures than what you set the knob to, preheat the oven 20 degrees below the recommended setting; place your clay item in the oven for 10 minutes before increasing the temperature to the regular setting. Set a timer to ensure that you don’t overbake. Do not use polymer clays for drinking or eating utensils because of the chemicals in them.